Rainwater Harvesting for Drylands and Beyond by Brad Lancaster

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Hand-Pump & Siphon Greywater System

Hand-Pump & Siphon Greywater System

This is a great system for obtaining greywater from an existing interior bathtub or shower which is currently without a greywater drain or access to the drains below the floor, and is located against an exterior wall. You pump the hand pump a few times, the siphon effect kicks in, and the greywater drains out to the landscape (fig. 1). (Note: The area to which you are directing greywater must be lower than the intake point of the hand pump for the siphon effect to work).

Fig. 1. Hand-pump-powered greywater drain. Tub drain is plugged when bathing. Once done bathing, hand pump is pumped about six times until the siphon effect kicks in, and a good flow of water drains out via the pipe and hose to the landscape.

Fig. 1. Hand-pump & siphon greywater system. Tub drain is plugged when bathing. Once done bathing, hand pump is pumped about six times until the siphon effect kicks in, and a good flow of water drains out via the pipe and hose to the landscape.

My neighbor Moses Thompson set up a really nice system in his and his wife Kelly’s home, a system which is an evolution of the one I feature in chapter 12 of Rainwater Harvesting for Drylands and Beyond, Volume 2. A big improvement is Moses’ use of a higher-end, higher-volume hand pump—a Dayton Hand Drum Pump, model 2UY14—rated for liquid temperatures up to 140º F (60º C), so hot greywater from a bath is no problem (figs. 2 and 3). (The first hand pump Moses used was not rated for hot water and failed.) The high-volume capacity of the Dayton pump drains the tub/shower in just 5 minutes. The pump is readily available online, with a current price (summer 2015) of about $80. [Note: We were contacted by the folks at Action Pump Co in Illinois in regards to their U.S.-made model #5000 manual siphon pump which is also rated to 140ºF and is available online, currently for about $30. This could well be a comparable alternative to the Dayton, although we haven’t tested it. If you decide to try out Action Pump’s model, we’d love to hear how it performs!]

Fig. 2. Dayton hand pump, full view

Fig. 2. Dayton hand pump, full view

Fig. 3. Dayton hand pump label

Fig. 3. Dayton hand pump label

Moses and Kelly just use a regular tub drain plug to plug the tub when bathing, then drain the tub with the pump.

Moses wisely avoided 90º bends in his pipe run, instead using 45º bends to get better flow. All was hard-plumbed with 1-inch PVC and then stepped down with a barbed fitting to connect to a conventional 5/8-inch (15-mm) diameter garden hose (fig. 1).

However, based on their experience using the system, Moses thought that a higher-quality, higher-volume (3/4-inch (20-mm)) garden hose would be better, because the cheaper, smaller-diameter hose kinked frequently. You can tell right away when you start pumping if the hose is kinked, as the flow stops and you have to go outside and unkink it.

All garden hoses kink, though, so to avoid kinks altogether use spa-flex PVC hose. You can get it in 1-inch (25-mm) diameter, and just about any color you like. Or to avoid kinks you can run the garden hose or spa-flex hose down the outside of the exterior wall, and once you hit ground level, transition the hose into a rigid-plastic-piped branched drain—just make sure the end of the hose is below the elevation of the pump inlet, so the siphon will work. (See Rainwater Harvesting for Drylands and Beyond, Volume 2, chapter 12, variations section, for details on how these systems interface.) If you do use only garden hose (no pipe), keep in mind that the longer the hose, the farther you can move the water, but when watering plants close to the greywater source, you have to roll up more hose without letting it kink.

In 10 years of use, the hose has never clogged. While Moses has very short hair, Kelly’s hair is long.

Each day, Moses moves the hose to a different plant in the yard (he rotates between four different zones) (fig. 4), though he also has the option of leaving the hose in place for a number of days when establishing a new plant. Regularly moving the hose distributes the greywater to multiple points and helps ensure the soil stays healthy, aerobic (oxygen rich), and odor-free. Whereas if all the greywater were always sent to the same spot, the soil could have become saturated, anaerobic (lacking oxygen), and stinky. Thus this is a good system for people that like to interact with their plants and water system. But if you are more of a hands-off person, you might be better off directing the siphoned water into a branched-drain system (like the Hand-Pump-Powered System featured in Rainwater Harvesting for Drylands and Beyond, Volume 2), which distributes the greywater to multiple plants without your needing to move any pipe or hose.

Figure 4. Hose coming out of bathroom wall. Hose is daily moved to a different plant/zone to keep soils healthy, aerobic, and odor-free. Photo credit: Moses Thompson.

Figure 4. Hose coming out of bathroom wall. Hose is moved daily to a different plant/zone to keep soils healthy, aerobic, and odor-free. Photo credit: Moses Thompson.

To make the system more convenient and joyous to use, Moses shortened the down tube near the inlet, so the pump hits water with the plunger in just one or two pumps (see fig. 5). Once that occurs, he pumps about six more times and a good flow of water siphons out on its own. More pumping was required pre-retrofit.

After Moses shortened the pump’s down tube by cutting out a section of its length, he used vinyl tubing as a coupling to reconnect the shortened tube to its inlet, because the shaft is not a standard PVC-pipe size (fig. 5). The vinyl is a little elastic so he was able to slide it over both ends for a good seal. If a tighter seal were needed, stainless steel hose clamps could be used around the vinyl tube.

Fig. 5. Vinyl tubing used as a coupling to reconnect the pump’s shortened down tube with its inlet.

Fig. 5. Vinyl tubing used as a coupling to reconnect the pump’s shortened down tube with its inlet.

The pump outlet (which goes off to the side, up near the handle) is also not a standard size, so vinyl tubing could be used there, too, to transition to PVC pipe. But what Moses did instead was to use a 1-inch by 1-inch (25-mm by 25-mm) PVC slip-coupling, with the pump outlet glued inside a short section of 1-inch (25-mm) PVC pipe. It wasn’t a perfect fit so he used a few extra coats of PVC cement. Though one advantage of connecting to the pump outlet with rigid pipe bracketed to the wall would be that the pipe would help hold the pump more steadily in place.

When asked to sum up 10 years of using the system, Moses reported, “It has worked so well we never installed a branched-drain system with three-way valve in the crawlspace under the bathroom floor, which had been my initial intention. The hand pump was intended to be an interim solution, and it just stuck.”

And as to whether or not he’d recommend it to others, he responded, “I’d recommend it to someone who has a little building/plumbing experience, someone who enjoys trial-and-error tinkering. It’s definitely a site-specific custom build, not an out-of-the-box kit.”

 

For more on this and other systems, read chapter 12 of Rainwater Harvesting for Drylands and Beyond, Volume 2—especially the Developing a Gravity-Fed Greywater System section.

Do you have an addition to this list? Let me know.

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The Umbrella: Spring Equinox 2017

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Spring Equinox 2017
Around here we like to rhyme with the seasons whenever possible. In this case, that means welcoming the fast-approaching beginning of SPRING (the Vernal Equinox (in the northern hemisphere) is March 20 this year in Tucson, and marks one of only two […]

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